Bromine vs UV Lamp: Better than Chlorine..?

[Daf-Tekno]

Dear Tubby Tellies,

I fitted a UV lamp (to kill more bacteria) but found it also kills off some of the chlorine too!
There appears to be a couple of ways to deal with this.

One suggestion is to convert my tub, not to salt water SWG, but to bromine salt water SWG.
This is because bromine will not be killed off by the UV lamp, like chlorine is.

Can anyone tell me if this is true?

I would've thought that they would both act in similar ways, i.e. both become weakened by exposure to UV.
But it sounds like this might not necessarily be the case.

Your thoughts would be appreciated.
- D

 

[chem geek]

Bromine is also broken down by UV, though not as quickly as chlorine with no CYA. However, if you have CYA in the water with the chlorine, then it should break down somewhat more slowly than bromine.

Why don't you disconnect the UV lamp and just use chlorine. Chlorine alone will kill bacteria very quickly and there is no need for the UV system.

 

[Daf-Tekno]

Hi ChemGeek,

Delta UV responded to me with this justification of a UV lamp's installation in a hot tub:

UV is useful on your hot tub because it eliminates the chloromines (which is chlorine gas that produces that chlorine smell)
Giardia can take up to 45 minutes to deactivate with chlorine, noro virus can take 30-60 minutes to deactivate
Cyrptosporidium can remain in your hot tub up to 10 days once introduced and is resistant to chlorine.

As Jacuzzi and MAAX Spas are both fitting UV systems as standard on their top-end tubs, I suspect there may be an element of truth to the additional anti-bacterial aspect of a UV lamp system.

Also, it cost a load of dosh, so I'm not particularly inclined to ditch it until I'm totally convinced it is of no use.
My line of thinking is have as many germ-defenses as possible: Chlorine, ozone, UV, SWG...

But I am open-minded, so will be altering my thinking as I see how my tub reacts to various set-ups.
- D

 

[chem geek]

Never, ever, believe what someone with a financial interest in what they are selling you has to say. It's not necessarily that they will lie, though some do, but rather that they will deceive. They will intentionally withhold materially important information that you need to know to make an informed purchase decision. Well not everyone does this, of course, but you should assume the worst while hoping for the best.

Look at this post that shows kill times for chlorine (vs. copper and silver, but you can ignore that) at an FC that is roughly 10% of the CYA level at pool water temperatures, so roughly equivalent to 0.1 ppm FC with no CYA. The active chlorine level in your spa will generally be higher when you add chlorine after a soak due to the hotter water temperatures. You can see that chlorine kills most pathogens very quickly.

They gave you specific examples where chlorine kills more slowly, but protozoan oocysts like Giardia and Cryptosporidium are not in your normal fecal matter. You would only get that in your spa if someone was sick with those parasites and had diarrhea. Unless you are talking about a commercial/public spa, such worries are serious overkill -- FUD to get you to buy equipment you do not need. As for noro virus, you are far more likely to get that kind of virus from someone via their secretions such as in food preparation (see this link).

There's nothing wrong with using either ozone or UV -- I was only responding to your complaint that it consumed chlorine. Ozone also consumes chlorine. If you really want these supplemental systems, then that's fine and you just need to add more chlorine to be able to maintain a level. That pretty much means adding chlorine every day or two which is no big deal if you soak every day, but if you only soak once in a while, say on weekends, then it's a PITA.

By the way, chloramines are NOT chlorine gas. They smell because of their specific chemistry -- some of the chloramines are volatile and they have specific odors. Generally you start your soak with only 1-2 ppm FC so not many chloramines build up -- it's mostly monochloramine from the ammonia in your sweat and urine and that's similar to taking a shower or bath with chloraminated water. It's after your soak when you blast with enough chlorine to handle your bather waste that more chloramines form and you can leave the cover off for a short while to air out the spa during that time and also some time before you next enter the spa.

 

[Tepelus]

UV light is a proved safety backup that bring the benefit of eliminating the chloramines. The increase chlorine consumption can be reduced by putting the UV light on a timer. I think is best to start the lamp when you enter the spa and stop it sometimes later. The unpleasant smell is the vapors of chloramines. These vapors are the toxic byproduct of chlorine disinfection. I use the UV lamp together with bromine in our swimming pool. The UV lamp creates also small amounts of ozone and that more than compensate the bromine destruction by UV light. The level of disinfectant can be kept at a lower level and the overall running cost for the 2014 season was more than reasonable.

 

[chem geek]

You know, I thought the same thing after sleeping overnight. Have a switch or timer so that you can have the UV on when you are using the spa and shortly afterwards. That significantly reduces the time it is on so the chlorine usage/consumption from the UV should be minimal, but the benefit will be there when you need it most. You really don't need the UV to be on in between soaks (except for the hour after your soak after you've added chlorine) because there is no introduction of new pathogens into the water and the chlorine alone will prevent any uncontrolled bacterial growth, especially on surfaces where the UV does absolutely nothing because pathogens on surfaces are not circulated to the UV.

UV is most useful for indoor pools where there is no sunlight. It can help control Combined Chlorine (CC) which can be a problem in such pools. In residential spas, it's more of a question because CC isn't usually an issue when the chlorine is properly dosed right after a soak, but if limited when it is on then the UV is a nice supplement. For outdoor residential pools, the UV is really superfluous due to the UV in sunlight and the low bather loads in residential pools. Perhaps if the pool is covered most of the time so not exposed to the UV in sunlight, then it will be more useful.

As for hydroxyl radicals, when chlorine (or bromine) breaks down from the UV in sunlight or from a UV lamp, it produces hydroxyl radicals that are powerful oxidizers. This is one reason why outdoor residential pools don't typically have issues with CC. See this post which talks more about this though in the context of ozone.

By the way, if one is concerned about disinfection by-products, note that brominated by-products are worse than the chlorinated ones (see this post).

 

[Tepelus]

The mentioned data in fact corroborate with the fact? that bromamines are efficient sanitizers while chloramines are not. Anyway chloramines are volatile and might be up taken by inhalation, while bromamines should be less volatile, therefore absorbed only through skin. This is in fact more dangerous since the bromamines might accumulate making a UV lamp imperative for covered pools and spas.

 

[chem geek]

The disinfection by-products of concern in what I linked to are not the inorganic bromamines (i.e. monobromamine). Chloramines and bromamines are airway irritants, but they are not generally considered to be cancer-causing. It is the brominated organics such as the trihalomethanes, the haloacetic acids, the haloacetomides, etc. that are of concern. These are not only volatile, but also absorb through the skin.

UV is a mixed bag with regard to disinfection by-products because it destroys some of them while creating others because it breaks some larger molecules down into smaller pieces and the chlorine or bromine then reacts with these smaller pieces. The latest info regarding UV and chlorinating is in this presentation being given today at the Worldwide Aquatic Health Conference that I am attending. For example, with L-Histidine, more inorganic chloramines are formed from UV though they are then also broken down by UV, more dichloroacetonitrile is formed from L-Arginine and L-Histidine, more cyanogen chloride is formed from glycine and uric acid which I show below:

https://www.troublefreepool.com/~richardfalk/pool/DBP_Toxicity/Glycine-UV.png

https://www.troublefreepool.com/~richardfalk/pool/DBP_Toxicity/UricAcid-UV.png

I'll ask Dr. Blatchley about UV and bromine though I don't think he has explicitly studies that.

Note that in low bather load pools and spas I'm not saying that these issues are so serious that you should avoid the use of the chemical, but you should not be under the misconception that bromine is better than chlorine with regard to its disinfection by-products.

 

[Tepelus]

Thank you Chemgeek for sharing these facts with us. Looking at these graphs one can easily see that these photoreactions are quite slow. In my filtration system a particle in the water will pass through the UV lamp in about 6 seconds. Since I run the system with one turnover per day, I can say that water is exposed to UV for 6 seconds every day. According to these graphs 6 seconds do not mean much. Of course I do not know if the fluence rate of the UV light source is similar to what I have, that is a 110W UV-C germicidal lamp. I can conclude that if the UV light source is similar to a commercial UV lamp, a UV germicidal lamp does not make the situation worse by increasing the amount of these chlorinated organics.

In the case of bromine, I think that the situation is even better since bromine is less reactive since one has to use monopersulfate to mitigate the buildup of organics in the pool or spa. May be I am wrong, but I think that bromine will generate less halogenated organics (amount). Myself I am more concerned with the formation of bromate in the pool water. I do not know how well the bromate molecule penetrates through skin, but with a molecular weight well below 500, it should penetrate quite well. O course it is a question of concentration since toxicity is strongly dependent of it.

 

[JasonLion]

There is always going to be some water that is not exposed to the UV lamp on any given day. Much of the water goes through the system once, some goes through twice (or more times) and some doesn't go through at all. Once you take that into account, it greatly increases the kill times related to the UV light, as the water that is not going through the pump doesn't have it's contaminates exposed to the light.

Also, while UV does indeed get rid of chloramines, chlorine does that also. UV is a bit faster at eliminating chloramines, but at residential usage levels the speed difference doesn't make any real difference. The chloramines will be taken care of by the next time you use the tub either way, unless you are having a large tub party.

 

[Tepelus]

Good point Jason Lion. Still I wander if the bromine will eliminate the bromamines or if the chlorine used for generating bromine can eliminate them. I believe that bromamines are less volatile than chloramines, remaining in water much longer.

 

[chem geek]

I spoke to Dr. Blatchley and he didn't think that the UV by-products issue would occur with bromine since the UV breaks apart the carbon-chlorine bond but not the carbon-bromine bond. So while the brominated organics are more toxic than the chlorinated ones, UV shouldn't make things any worse.

As for the bromates, you don't need to worry about them because as described in this paper they don't absorb readily through the skin (mostly because they are negatively charged) and hydrophilic (it's neutral small organics that tend to penetrate through the skin due to the skin's multiple hydrophobic and hydrophilic layers). Bromates are also not volatile so they are only an issue for drinking water and you don't drink spa water.

 

[JamesW]

Chem Geek, do you think that brominated organics and bromates would show up on a combined bromine test? Would there be any value in doing the test?

 

[chem geek]

The bromates for sure would not show up in the combined bromine test, but the brominated organics would. So when using a chlorine test kit, the FC will register both the hypobromous acid as well as inorganic bromamine, namely monobromamine, but it won't measure the organic bromamines. The potassium iodide in the R-0003 will react with the organic bromamines so will register in the CC test. However, the amount of CC that would be dangerous for some of the organic bromamines is too small to be seen even with the 0.2 ppm resolution using a 25 ml water sample. 100 µg/L would be 0.1 ppm, for example, and would be a 1 in 40,000 lifetime cancer risk (based on drinking water assessments) for bromoform, a 1 in 6000 risk for bromodichloromethane, and a 1 in 4000 risk for dibromochloromethane.

Clearly if one measured high CC levels, then there would be cause for concern, but more than likely they won't and unfortunately even if one did one couldn't know which type of brominated organic they had. A complete trihalomethane test distinguishing the different chemical species runs around $130. I had that done for my chlorinated pool, just out of curiosity.

 

[JamesW]

Ok, thanks. I sometimes get a reaction when I do a combined bromine test. However, it's not something that I have tested in a controlled way that could help identify what was reacting with the iodide. The reaction is especially strong after adding sodium hypochlorite, so it might be chloramines that have been created.

 

[chem geek]

If the sodium hypochlorite is added after a soak and if there isn't enough bromine in the water to last through the soak, then it's probably chlorine combining with ammonia to form monochloramine since that occurs very quickly (less than a minute even when CYA is present) and is faster than chlorine's oxidation of bromide to bromine.

 

[Daf-Tekno]

Hi y'all,

Wow! What a barrel of monkeys I've opened!

I have my UV lamp on 24 / 7 with the circ pump, as the bulb wears out faster if switched on & off regularly.
Delta recommend minimising the amount of power interruptions to help with bulb life.

An option would be to have it linked to the ozonator circuit, but as this switches off during bathing, and is usually on 24 / 7 the rest of the time (don't know why this is, maybe ozone gas is perceived as dangerous so it is disengaged during spa use..?), this would be the exact opposite to your suggestion earlier of having it on during bathing and off the rest of the time.

If having it on only during spa use is the professionally recommended use of a UV lamp, then I could rig the power feed to come off one or both of the main pump feeds instead of the circ pump feed.

Did Dr Blatchley mention anything about this aspect of UV lamp use, ChemGeek..?

Thanks - D

 

[chem geek]

The ozonator is turned off during spa use precisely for the reason you stated, that ozone outgassing is perceived to be dangerous.

If you have an ozonator in this spa as well, then why do you think that it is the UV that is destroying the chlorine? It is known that ozone reacts with chlorine to form chloride and chlorate (see Chemistries of Ozone for Municipal Pool and Spa Water Treatment). If you use the spa every day or two, then ozone will oxidize bather waste and the net result is usually a lowering of chlorine demand, but if you use the spa less frequently, then ozone will increase chlorine demand in between soaks. Specifically, whereas normal 24-hour chlorine usage between soaks (i.e. without bather load) is 25% or less in a hot spa, with ozone it is usually 50% or more. On the other hand, chlorine usage from bather load is cut at least in half when ozone is used.

I think you should first confirm that it is the ozone rather than the UV that is the source of your extra chlorine demand. If you can turn off each individually (or turn off both, measure a baseline, then turn on one at a time measuring each separately) then that would be best. This needs to be done without bather load.

Note that if you were to go to using bromine, then ozone will create bromine from the bromide bank but will also use such bromide bank up over time (creating bromate) so you'd need to replenish the bromide bank. Unfortunately, testing for the bromide level is non-trivial.

Dr. Blatchley, as a scientist, generally doesn't make recommendations but just reports results, but we didn't discuss the option of power-cycling UV to optimize its use. Generally, the loss of chlorine from UV is considered to be low compared to the amount of chlorine needed to handle bather load in commercial/public pools.

 

[Tepelus]

A UV light bulb has a life span of around 9000 hours. Turning the lamp on and off daily is the norm. Turning the lamp on-off more than once every day may reduce the life span of the lamp to some extent (burning hours). If you are going to have the lamp on all the time you will have to replace the UV tube every year even if it seems to work since the UV output decreases with time.

 

[Daf-Tekno]

Hi there,

I unplugged the UV lamp, and my chlorine consumption has decreased massively!

With the UV lamp on, I had FC of 4.0 one evening, but the next day it was at 1.4 (no bather use).
With the lamp unplugged, an FC of 3.0 one evening went to 6.6 the next day (no bather use).

Ozonator engaged on both occasions.

I am currently working on constructing a control system via 2 solenoids and timers that will allow the UV lamp to come on only when the tub is in use, and then to continue being on for a period of time afterwards, after which it will switch off until the next tub use.

How long should the UV remain on after bather use? 30 mins? 1 hour?

Thanks - D